The long term objective is to understand the physiology and pharmacology of the neural system that transmit and modulate pain. The specific aim is to determine the elecrical properties of isolated spinothalamic and trigeminothalamic cells (dorsal horn projection cells), and the mode of actions of a number of transmitter substances on these cells. The objectives of these experiments are (1) to determine the voltage dependent properties of identified projection neurons and (2) to characterize the actions and interactions of amino acids, peptides and biogenic amines on these cells. The ionic currents of identified single projection cells will be measured under voltage clamp conditions. Patch pipette voltage clamp technique will be used. The fundamental knowledge obtained from these experiments will be essential in defining the mechanisms of action of the putative transmitters in spinothalamic cells.